1. Field of the Invention
The present invention relates to a communication device, such as a communication terminal and a method of controlling its heat generation, and in particular, to a communication terminal equipped with a function of preventing overheat in the whole or a part of portable communication terminal, and a method of controlling its heat generation.
2. Description of the Related Art
In recent years, a problem which has arisen easily is that the surface temperature and internal temperature of a portable communication terminal becomes high at the time of charging of a videophone or the like in a heavy load state, with the miniaturization and effort-to-high-performance of the portable communication terminal. Here, in order to prevent the temperature rise of a portable communication terminal, it is necessary to remove a cause of heat generation. As conventional method of controlling charging heat generation, a method of stopping charging at the time of high temperature detection and a method of performing charge control by the present temperature of a battery or a terminal are proposed. However, the former method has a problem that charging operation stops. In order to solve this problem, the method of implementing a measure against charging heat generation at apparatus temperature is necessary.
Then, in order to implement the measure against the charging heat generation at the apparatus temperature, a portable communication terminal equipped with a battery charger which prevents the excessive heat generation of a battery is described in, for example, Japanese Patent Laid-Open No. 8-149711. In a battery charger which calculates the internal temperature of a battery on the basis of the detection result of first temperature detected inside a battery pack, and second temperature detected within the battery charger, measures the time elapsed from a charging start, determines a rise rate per unit time of temperature inside the above-mentioned calculated internal temperature of the battery when measuring time becomes predetermined time, and ends charging when the rise rate exceeds a reference value, this battery charger has the structure of selecting the predetermined time until determining the internal temperature rise rate of the battery, on the basis of the first and second temperature detection results at the time of the charging start.
The portable communication terminal equipped with this battery charger determines a termination of charging according to the internal temperature rise rate of the battery, can correct the time until an temperature rise rate is measured, and the reference value of the temperature rise rate according to the remaining heat of last charging, environmental temperature, and a type of the battery, and a heating value of the battery, and suppresses the excessive heat generation of the battery by eliminating the excess and deficiency of charging.
Thus, the conventional portable communication terminal equipped with the above-mentioned battery charger controls heat generation by controlling the charging of the battery according to the measured present temperature and present temperature rise rate based on the temperature within the terminal.
Another conventional portable communication terminal equipped with a battery charger is described in Japanese Patent Laid-Open No. 2002-218026. This portable communication terminal reduces charging current by a constant value if it has a call during charging. This terminal solves the problem that heat generation increases during charging with a call comparing to during only charging.